Design of field-plate terminated 4H-SiC Schottky diodes using high-k dielectrics

Silicon carbide (SiC) field-plate terminated Schottky diodes using silicon dioxide (SiO2) dielectric experience high electric field in the insulator and premature dielectric breakdown, attributed to the lower dielectric constant of the oxide. To alleviate this problem we explore the use of high-k dielectrics, silicon nitride (Si3N4) and sapphire (Al2O3), on 4H-SiC by numerical simulations using Medici. The simulation results show significant improvement in blocking voltages by as much as 30% and much lower electric field within the dielectrics. There is also a slight reduction in the specific-on resistance (Rsp-on) and a small increase in the forward current density due to the formation of an accumulation layer in SiC where the metal overlaps the dielectric. This effect is enhanced with increasing dielectric constant and decreasing dielectric thickness for a given dielectric.